Improved viral screening assays and more intensive questioning of donors for high-risk behaviors have resulted in dramatic declines in the rates of transfusion-transmitted hepatitis and AIDS. Nonetheless, there is need for continued vigilance of the safety of blood supply. This study aims to enroll blood donors and prospectively followed blood recipients in order to establish active surveillance for a multiplicity of potential blood transmitted infectious agents and establish a repository of linked donor and recipient samples so that newly emerging infectious agent can be rapidly evaluated for their threat to the blood supply. This study has thus far enrolled 1605 patients; 1005 from NIH and Suburban Hospital and 600 from Children's National Medical Center. We have complete serial sampling on 1028 (64%) patients and partial sampling on 176(11.0%) patients. 332(20.7%) patients have either died, or were lost to follow up and 69 patients are in active follow up. For the 2104 patients with at least partial sampling, there have been approximately 6000 blood exposures. There has been no transmission of HCV, HBV, HIV or HTLV observed. There has been one definite transfusion-related transmission of parvovirus-B-19. Using unlinked donor samples we have found the prevalence of antibody to EBV to be 88% for anti-EBVCA IgG, 47% for anti-EBVNA and 0% for anti-EBVCA IgM; the prevalence of anti-CMV IgG is 44% and is 2% for anti-CMV IgM. We have tested 500 donors for anti-HHV-8 against two HHV-8 epitopes. The average seroprevalence of anti-HHV-8 is approximately 15%. Using an unlicensed but well-validated EIA, the prevalence of antibody to the hepatitis E virus was 21.8% in 916 donor samples obtained in 2006, but fell to 16% in 1023 donor samples obtained in 2012. Only 0.4% of samples were positive for IgM anti-HEV in both time periods and none of the antibody positive samples were HEV RNA positive. In a prospective follow-up of 362 blood recipients, no HEV transmissions have been observed. We continue to investigate the transfusion risk of CMV, HHV-8, HBV, HCV and HIV by molecular techniques. We found that 47(4.7%)of 1000 recipients tested HHV-8 DNA positive in their post-transfusion sample,but most were also positive in their pretransfusion sample; hence there were only 6(0.6%)molecular conversions and based on pre-transfusion serology, only one possible new HHV-8 infection that could not be confirmed subsequently. Similarly, there were 34(3.5%) molecular conversions for CMV DNA, but based on the presence of pre-transfusion antibody, all of these appeared to be CMV reactivations rather than new infections. Among 924 recipeints analyzed for parvo-virus B-19, there was one molecular conversion (0.1%)that represented one transfusion transmitted infection proven by phylogenetic analysis of the virus in both donor and recipient. This represents one of only four other documented cases of B19 virus transmission by single-donor blood components and the case was published in the journal Transfusion. Thus far, the proportion of patients that develop new infections post-transfusion is small although reacttivation of CMV infection is relatively common. Also, even a single observed case, as for Parvo B-19, when extrapolated to the 15 million blood products transfused per year in the U.S., potentially represents thousands of transmissions nationwide. As expected, there were no identified transmissions of HBV, HCV or HIV. In light of epidemics of dengue, zika virus and chikungunya virus in South America and the Caribbean, we have begun a surveillance of blood donors who travelled to these areas and will closely follow any that test positive for these agents. We are also developing methods to test for all three agents simultaneously. We have completed a study assessing the transfusion risk of the hepatitis E virus (HEV). This agent, previously thought to cause only acute resolving hepatitis and to be rare in industrialized countries, has now been shown to sometimes result in chronic liver disease and isolated cases of blood transmission have been reported in industrialized nations. Our testing of blood transfusion recipients revealed 2/362 (0.06%) possible antibody seroconversions. Neither recipient was found to be HEV RNA positive at any time point in the study. Further investigation of linked donor samples, found that in one case, antibody positivity was caused by passive transfer of IgG from a donated unit with high titer anti-HEV. Overall, this study did not find any cases of transfusion-transmitted HEV infection despite the high prevalence of anti-HEV antibody in the donor population. These findings were published in the journal Transfusion in October, 2013. We have completed our study of transfusion-associated microchimerism (TA-MC) in this TRIPS cohort and have now tested 431 adult and pediatric female blood product recipients for persistence of donor leukocytes as determine by detection of Y chromosome. We evaluated persistence of TA-MC in a non-trauma setting where all blood is leukoreduced and at least half the blood is irradiated. Of the 431 recipients tested, 14.3% (12/84;5 adults and 7 children), demonstrated very low-level, but reproducible MC. However, development of persistent high-level MC was not demonstrated in any of 431 adult and pediatric blood recipients. The risk of TA-MC appears dependent on the clinical setting, being rare in routine transfusion and high in patients sustaining severe trauma. The preliminary data was presented at the 2010 annual meeting of the American Association of Blood Banks (AABB) and was published in the journal Transfusion, October 2011. In addition, we collaborated with Dr. Philip J. Norris from Blood Systems Research Institute (BSRI) in San Francisco, California to evaluate human leukocyte antigen (HLA) alloimmunization in recipients of leukoreduced (LR) and non-leukoreduced (non-LR) blood using newer, more sensitive antibody detection assays. Pre-transfusion and serial post-transfusion (4, 8, 12, & 24 wk) samples from 20 TRIPS recipients of LR blood were tested and compared to 29 recipients of non-LR blood provided by the Transfusion-Transmitted Viruses Study (TTVS). A substantial proportion of subjects possessed pre-transfusion HLA Abs in both cohorts studied (20 of 29 in TTVS, 8 of 20 in TRIPS). Applying a sensitive HLA Ab test revealed high levels of baseline alloimmunization in the TTVS and TRIPS cohorts and frequent alloimmunization even in recipients of LR blood. An abstract detailing the results from this study was presented at the 2010 annual meeting of the AABB and a manuscript has been published in the journal Transfusion, June 2013.